Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.58	12.507%	$134.5359	$134.54	$134.55	$134.50
Purchase #2	$160.58	12.182%	$180.1419	$180.14	$180.15	$180.10
Purchase #3	$169.87	12.641%	$191.3433	$191.34	$191.35	$191.30
Purchase #4	$243.40	5.122%	$255.8669	$255.87	$255.85	$255.90
Purchase #5	$75.75	13.327%	$85.8452	$85.85	$85.85	$85.80
Purchase #6	$131.93	6.649%	$140.702	$140.70	$140.70	$140.70
Purchase #7	$124.31	5.472%	$131.1122	$131.11	$131.10	$131.10
7 purchase totals =	$1,025.42		$1,119.5474	$1,119.55	$1,119.55	$1,119.40